Annealing and pickling of hollow metal articles



J. CURRAN Jan. 9, I940.

ANNEALING AND FICKLING OF HOLLOW METAL ARTICLES eats-Sheet 1 Filed Jan. 12, 1959 In ve/7f0r Jo/an Curran 5 Mia v M y M M Awe J. CURRAN ANNEALING AND PICKLING OF HOLLOW METAL ARTICLES Jan. 9, 1940.

Filed Jan. 12, 1939 3 Sheets-Sheet 2 m mm I! I! 'I II MI \mm 1 I n N mm mm m m M n N G 6K 6N E on m G QR m QR k R In venfor Z Job/7 Cur-ran,

Wzgv By W M A 7.

J. CURRAN 2,186,856

ANNEALING AND PICKLING 0 ?v HOLLOW METAL ARTICLES Jan. 9, 1940.

3 vSheets-Sheet 3 lnvenfor':

John Cur/"ah 1 I i. w 0333810 I I 4 3 W 1! 11 1/ I I z r: I 1 I i m I I I v 1 mm L mm 1L M. mm 1 a w 9 a Patented Jan. 9, 1940 PATENT OFFICE ANNEALING AND PICKLIING OF HOLLOW METAL ARTICLES John Curran, Cardifl, Wales Application January 12, 1939, Serial No. 250,625 In Great Britain March 4, 1937 4 Claims.

This invention relates to the annealing or normalising and subsequent pickling of metal articles and is especially applicable to the annealing and pickling of cartridge cases.

An object of the invention is to provide an improved apparatus for annealing and pickling hollow metal articles so that the manufacture of such articles can be accelerated while at the same time the necessity, which arises especially when cartridge cases are treated, for efliciently treating the articles is adequately met.

Another object of the invention is to provide a conveyer type heating furnace which comprises an improved conveyer for moving articles throughthe furnace.

A further object of the invention is to provide improved apparatus for pickling metal articles.

A still further object is to, provide improved apparatus for pickling metal articles which is applicable to articles of widely different form. Yet another object is to provide a low temperature annealing furnace whereby metal articles can be more expeditiously and economically heat treated than was hitherto practical.

Another object is to provide apparatus for heat treating and subsequently pickling and washing cartridge cases whereby the manufacture of such articles can be accelerated, while the apparatus can be efliciently operated in less floor space than was hitherto practical.

Hitherto the treatment of metal articles has included pickling the articles after annealing by immersing, usually manually, the articles in a bath of pickling acid and although this method is both'laborious and time-wasting it has, especially in the case of. cartridge cases, hitherto been considered necessary in order that all the parts of the articles should be properly subjected to the action of the acid. In the case of flat sheets an adequately uniform distribution of pickling acid can more easily be effected by spraying with oppositely directed horizontal sprays as has already been proposed.

For the annealing and pickling of hollow articles the present invention, in one aspect thereof, provides means for simultaneously spraying both the interior and exterior surfaces of the articles'and a continuously moving conveyer for carrying the articles through the pickling chamber after the articles have emerged from an annealing furnace.

The invention further provides an annealing furnace and pickling apparatus which comprises continuously moving conveyor means for carrying articles progressively through the furnace and a pickling chamber and means for spraying pickling acid on to the articles while the latterare supported on the conveyer.

Further featuresof the invention will be described in the following description with reference to the accompanying drawings which illustrate apparatus for treating brass cartridge cases of 3.45" calibre and in which- Fig. 1, is a sectional side elevation of an annealing electrical resistance furnace and an endless conveyer;

Fig. 1a is a similar view of pickling and washing chambers and should be read in. conjunction with Fig. l and is arranged on the right thereof;

Fig. 2 is a cross-sectional view on the line 2-2 of Fig. 1;

Fig. 3 is a cross-sectional view on the line 3-3 of Fig. 1a;

Fig. 4 is a sectional view of part of the apparatus shown in Fig. 3;

Fig. 5 is a fragmentary plan view of the conveyer of Figs. 1 and 1a;

Fig. 6 is a cross-section of the conveyer of Fig. 5 and Fig. '7 is a fragmentary view illustrating a method of avoiding welds in the conveyer;

Fig. 8 is a part section and part elevation of a modified form of electrical resistance furnace intended for low temperature annealing;

Fig. 8a is a view similar to Fig. 1a and is to be read as being arranged on the right of Fig. 8, and

Fig. 9. is a cross-sectional view on the line 9-9 of Fig. 8.

Referring first to Figs. 1 to 6, a furnace l is constructed of insulating material 2 and a refractory lining 3. Ports 4 in the furnace side walls admit resistance heating elements 5 which extend across the upper and lower parts of the furnace space. The element terminals 5a project outside the furnace walls and the different elements are interconnected by straps (not shown) which are normally protected by covers 6. Removal of the covers permits of ready detachment of the straps and the construction illustrated renders possible easy and quick removal and replacement of the elements 5. The rating of the elements is such that a higher temperature is attained in the front part (shown on the left of Fig. 1) of the furnace space than in the succeeding portion. In the example described the temperature in the front part is 650 C. and in the remainder 630 C. By arranging the elements in banks, control of the current therethrough for the purpose of regulating the furnace temperature can readily be accomplished by known methods, for example with the use of pyrometers. At the rear end of the furnace i is an unheated insulated extension la which serves to prolong the annealing treatment.

Through the furnace space there passes an endless conveyer 1 which is constructed of a number of parallel strips 1a made of nickel-chrome. In order to avoid undesired strains in the strips, the drums 8 over which the conveyer passes are made of a comparatively large diameter in order to avoid sharp bending of the nickelchrome strips. The various strips 1a are spaced by cross members lb as shown in Fig. 5, the members lb being secured to the strips 1:1 by bending and clamping as illustrated in Fig. 6. The cartridge cases which pass out of the rear end of the furnace I move next, while still hot,

into a pickling chamber 9, entering this chamber while they are at a temperature of about 200 C. The cases, which rest on their mouths throughout their journey on the conveyer-I, are subjected in the pickling chamber to the action of a pickling acid. With cases made of :30 brass a satisfactory pickling acid is a solution of sulphuric acid in the proportion of 2.5 parts by weight of acid of specific gravity 1.75 at 60 C. to parts of water. The acid is maintained by any suitable known method at a temperature in the range 60 to 100 C. and is sprayed on to the cartridge cases from perforated pipes I 0. The perforations in these pipes are so arranged that the acid issues from them in different directions towards the objects to be pickled, so that all the surface of these objects receives the acid. The acid falls from the objects to the bottom of the chamber 9 and passes thence via a filter pipe II to a pump l2 by which it is returned to the spray pipes l0. Interruption of the circulation of the acid due to clogging of the perforations in the pipes 10 is liable to. be caused by solid particles which enter the circulating stream and it has been found that this trouble can be avoided by making the holes in the filter pipe I I slightly smaller than those in the spray pipes III. In an actual construction the perforations in the spray pipes were in diameter and those in the filter pipe %4" diameter. A reservoir, not shown, is connected in the circulating system and in order to maintain the quantity of acid in circulation at the proper volume, a continuous slow supply of fresh acid is preferably introduced to the reservoir by a pipe having a calibrated orifice which is submerged in the acid in the reservoir. The conduits which carry the acid solution are made of a suitable known material resistant to the acid used and a hard vulcanized rubber material such as that known under the trade name Dexonite may be used for the pipes in the chamber when sulphuric acid solution is used. The spray P pe l 0 are secured in the manner illustrated in detail in Fig. 4. In this figure is shown a main block I! having bores which intersect at right angles. Two of the bores communicate with the spray pipes II and one of these bores may also communicate with a flanged pipe H for commimication with the pump l2. The blocks I! located on the side of the chamber 9 opposite to that on which the pump I2 is placed are connected to solid flanged members IS. The pipes l0 and the members I and I! are secured to the blocks II by ferrules l6 which are in screw-threaded engagement with the blocks and which engage over flanged portions l'la on sleeves I! which screw on to the pipes II or the members H, 15

respectively. A solid plug l8 screws into the block l3 and may be removed to clean out the pipes It). A steel washer I9 is welded to the chamber and protected by a covering of acid-resisting material and is used for securing the member M to the chamber between the flanged portion of the members l4, l5 and the walls of the chamber 9. With the exception of the washer I9 all the other parts described are of the material known under the trade name Dexonite or other suitable acid-resisting material.

From the pickling chamber 9 the cartridge cases pass directly into a washing chamber 20 which may be compartmented and in which they are sprayed with a washing liquid, for example water, by apparatus similar to that in the pickling chamber. In the case of the washing apparatus, however, the water may be discharged to waste instead of being circulated back to the spray pipes by the pump 20a. On emerging from the washing chamber 20 the cartridge cases are ready for a succeeding operation, such as a pressing operation. It will be observed, therefore, that if a press is located at the front of the annealing furnace l the operative at the press can place the cartridge cases, or other articles, upon which he has worked, on the conveyer 'l and, therefore, no operative is required until the articles emerge from the washing chamber 20. If the next press is arranged adjacent the washing chamber, the operative at that press can pick up the issuing articles and place them in his machine and when known automatic apparatus is employed to regulate the heat of the furnace, and the temperature of the pickling acid, no otheroperatives are required. When the presses are arranged in line an operative at the rear end of the conveyor 1 may be employed to place the washed articles on a simple band conveyer which conveys them to the next press. -As compared with lmown methods of manufacturing cartridge cases, the present invention. therefore, oflers considerable advantages.

In order to avoid welding the ends of the strips 1a they may be bent over as shown in Fig. '7 and secured together by a bridle or clamp 10 which holds the bent up ends closely together or with only slight clearance between the bent up portions.

Instead of nickel chrome strips arranged to form a single conveyer 1, a conveyer formed by parallel steel ropes may be used to pass through the furnace and the articles may be picked up from these ropes by rubber covered ropes which form a conveyer which carries the-articles through the pickling and washing chambers. Such an arrangement is illustrated in Figs. 8 and 8a which show diagrammatically a low temperature annealing furnace constructed to give the flnal annealing and cleaning treatment to a shaped cartridge case which is otherwise ready for attachment of its cap and filling.

In the arrangement of Figs. 8-9, the furnace 2] is arranged in three zones or compartments separated by party doors 22, 23 which, with the doors 24 at the inlet and outlet, are arranged to be simultaneously raised and lowered by motors, for example electric motors, which are not shown. Sand seals 25 are provided where the connections to the party doors 22, 23 pass through the roof of the furnace. All the doors are protected by heat insulating material while the furnace itself is lined with similar material 26 disposed within a steel casing 27. It will be observed from Figs. 8 and 8a that the third zone is approximately three times as long as each of the first and second zones. The annealing process is carried out as follows: The manufactured cartridge cases are arranged in batches 29 which are placed successively on the conveyer 29 in front of the furnace while the conveyor is stationary. In due course the doors 22-24 are opened and the conveyer 29 is started so that the waiting batch moves into the first furnace zone. During this movement of the conveyer 29 when the furnace has been in operation for a suificient period, as will be recognised, a batch of cases will emerge from the rear of thethird compartment while other batches move on within the furnace, e. g. a batch in the first zone moves into the second and so on. In the first compartment the cases are raised to a'temperatureof approximately 130 C. while a stream of air is passed over the articles by means of a fan 30 arranged on the roof of the furnace. This air is circulated in a closed circuit over the elements 5 and the cases by ducts 3| in the furnace side walls and roof which communicate with the outlet of the fan 30 and ducts 32 in the roof which lead to the inlet of the fan. A fan 33 serves to circulate air through similarly arranged ducts in the second zone in which the cases are raised to a temperature of approzdmately260 C. In the third zone the cases are maintained at this last-mentioned temperature and a fan 33a is also provided to maintain a stream of air in this zone, the purpose of the air streams in each zone being to ensure that the cases are heated uniformly. After the batch has remained about 20 minutes in the first zone, the fans are stopped, the various doors opened and the conveyer 29 is started to move the bath from the first zone into the second, the other batches also moving forward. .The dimensions of the openings normally closed by the doors are arrangedso that as small clearances as are practical are left between the batch of. cases and the walls at the various openings in order that the opening of the doors should have the minimum effect on the thermal conditions inside the various zones andto this end the speed of the conveyer is arranged so that little time is occupied in moving the batches.

When the batches have been moved the conveyer is stopped, the doors are closed and the fans restarted. After treatment in the furnace a batch arrives at the end of the conveyer 29 on which it rests for a cooling period of twenty minutes. At the end of this period it is moved on to a second conveyer M which is formed of rubber covered ropes or other suitable material which at the forward end of the conveyer are interleaved with the ropes of the conveyer 29. The conveyer 34 moves more slowly than the conveyer 29 and passes the cases through pickling and washing chambers 35 and 38 which are similar to those described with reference to Figs.

As the conveyer 34 moves more slowly than the conveyer 29 while it passes the cases through the chambers 35, 36 it is temporarily driven at the speed of the conveyer 29 while the latter moves and is then slowed down.

On leaving the washing chamber 36 the casesare ready for polishing and any other superficial treatment necessary.

I claim:

1. Apparatus for heat treating and pickling hollow metal articles which comprises a heatingfurnace having an inlet and an outlet, a pickling to both the interior and exterior surfaces of the articles, while said articles are in the pickling chamber.

2. Apparatus for heat treating and pickling hollow metal articles which comprises a heating furnace having an inlet and an outlet, 2. pickling chamber of acid-resistant material having an inlet adjacent to the outlet of the furnace, a washing chamber forming a longitudinal extension of said picklingchamber, conveyer means constructed of nickel-chrome for carrying articles through said furnace and therefrom while unquenched directly into and through said pickling and washing chambers, liquid discharging means for spraying pickling acid on to both the interior and exterior surfaces of the articles while the articles are in the pickling chamber, and liquid discharging means for spraying washing liquid on to the said interior and exterior surfaces while the articles are in the washing chamber.

3. Apparatus as claimed in claim 1 wherein said conveyer means comprises a number of strips made of nickel-chrome, the'strips being parallel to thelength of the conveyer and spaced from one another by cross members secured to the strips by bending and clamping.-

4. Apparatus for heat-treating and pickling metal articles which comprises a furnace having an inlet and an outlet, a pickling chamber of acid-resistant material having an inlet directly adjacent to the outlet of the furnace, conveyer means constructed of nickel-chrome for carrying the articles through said furnace and therefrom while still unquenched directly into and through the pickling chamber, perforated spray members in said pickling chamber arranged to direct pickling acid towards the article in diflerent directions, a pump, a perforated filter member which communicates with the pump for return- 2 than those in the spray members.

JOHN CURRAN. 

